A reagent holder is disclosed in U.S.A. Pat. No. 3,999,948 for performing fluoro immunoassays. This reagent holder includes an elongated shaft with an examination surface area at one end where an immunofluorescent sample is supported in an instrument during examination. A preferred form of the reagent holder is shown in FIG. 13 of U.S. Pat. No. 4,144,452 where a cam surface on one side of the reagent holder cooperates with a detent in an examination instrument to retain the reagent holder in an examination location in the fluorometer.
An improved form of fluoro immunoassays has been developed in U.S. Patent Application Ser. No. 943,314 filed Sept. 18, 1978 where two test surfaces are provided on the same reagent holder and accompany each other through an immunoassay procedure. In accordance with this invention, an improved reagent holder is provided for performing the improved method in the equipment which used the original single sided reagent holder.